Method of maintaining a data log related to a Programmable Logic Controller (PLC)

ABSTRACT

Certain exemplary embodiments can provide a method for utilizing a memory cartridge connected to a Programmable Logic Controller (PLC). The memory cartridge can comprise a plurality of memory segments. The method can comprise a plurality of activities comprising: providing a default identifying stamp for records in a data log file, a structure for the data log file stored separately from the data log file in the memory cartridge, and obtaining a request to provide the data log file.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of, claims priority to, andincorporates herein by reference in its entirety, pending U.S.Non-Provisional patent application Ser. No. 10/685,821 titled “Methodfor Utilizing a Memory Device for a Programmable Logic Controller(PLC)”,filed 15 Oct. 2003, which claims priority to the following U.S.Provisional Patent Applications:

60/436,252, filed 23 Dec. 2002, and

60/436,249, filed 23 Dec. 2002.

BACKGROUND

Commercially available programmable logic controllers (PLC's) can besupplied with a memory device for storage. The memory device, which canbe a memory cartridge, is most often an electronically erasableprogrammable read only memory (EEPROM) device. Common methods of usingthe memory cartridge include the storage of PLC configuration andprogramming information.

U.S. Pat. No. 5,727,170 (Mitchell) allegedly cites: “[t]he PLC has auser configurable protocol port attached thereto. Briefly stated, at thePLC communication port or as a result of a user program or I/O event, aspecial flag bit may be set which thereby allows the communication portto be activated. This is done by the flag bit causing an interrupt tooccur in the PLC user program which allows a user to communicate with auser specified protocol scheme rather than the normalcommunication/programming protocol when this special bit is not set.”See Abstract.

U.S. Pat. No. 5,485,590 (Hyatt) allegedly cites: “[a] module interfacesa programmable controller to several serial communication networks overwhich data may be exchanged according to different protocols. A modulehas a central controller and a separate port circuit for each of thenetworks. Each port circuit includes a microprocessor and a sharedmemory to which both the central controller and the port microprocessorhave access for the exchange of data. The central controller transfersdata from the shared memories to a module output coupled to othercomponents of the programmable controller. A removable memory cartridgestores a plurality of programs for execution by the port microprocessorsto exchange data over the networks using different communicationprotocols. Configuration data is stored in the module defining whichprogram is to be transferred from the memory cartridge into the sharedmemory of each port circuit. Protocol parameter configuration inquiriesare stored for each program so that the user can be queried to selectvalues for the parameters of the communication protocol used by theprogram.” See Abstract.

U.S. Pat. No. 5,991,510 (Beaulieu) allegedly cites “A robot drive hasoperating and configuration parameters at an installation locationstored in an easily removable storage device on the drive, or nearby, sothat special data, such as that associated with arm design and systemlayout, including taught stations, can remain associated with the driveand installation whereby the drive system can be installed or replacedin minimal time since the storage device does not need reprogramming.This removable storage device, in the form of a static memory or MasterKey, e.g., a Dallas Key or E Prom or the like, may be affixed to therobot body or off board nearby, and may store arm design parameters,programmed while on the robot body or off-line, and becomes a uniquepart structured for manufacturing with respect to the arm set design.Further, nominal system layout parameters can be prestored in the Key,and when this Key is affixed to the robot drive, the robot automaticallyhas the information regarding both arm design and system layout, whichwill help avoid collisions and provide a starting point for the fineteaching of the transfer stations. Additionally, the fine locationparameters for each transfer station may be stored in the Key when therobot is installed. Thus, the Key will contain all the informationneeded to make a robot unique to a unique system, and when a robot driveis replaced, by affixing the original Key to the new robot or nearby, itwill assume all of the parameters of the initial robot.” See Abstract.

U.S. Pat. No. 4,937,419 (Kolodziej) allegedly cites “[a] programmableweld and machine controller for use in controlling a welding machine.The controller includes a central processing unit containing a storedcontrol program connected to a memory which operates both the weldingoperation of the machine as well as the operation of the machine itself.The controller receives inputs from the machine in its variousoperational states as well as a data entry and display unit and acurrent monitor of the welding operation which generates outputs througha heat controlled output to activate a firing circuit to control thewelding operation. Back-up of the memory program may be attained throughan accessory port to a memory back-up storage unit.” See Abstract.

SUMMARY

Certain exemplary embodiments can provide a method for utilizing amemory cartridge connected to a PLC. The memory cartridge can comprise aplurality of memory segments. The method can comprise a plurality ofactivities comprising: providing a default identifying stamp for recordsin a data log file, a structure for the data log file stored separatelyfrom the data log file in the memory cartridge, and obtaining a requestto provide the data log file.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention and its wide variety of potential embodiments will be morereadily understood through the following detailed description, withreference to the accompanying drawings in which:

FIG. 1 is a block diagram of an exemplary embodiment of a system 1000;

FIG. 2 is a block diagram of an exemplary embodiment of a data structure2000;

FIG. 3 is a flowchart of an exemplary embodiment of a method 3000;

FIG. 4 is a flowchart of an exemplary embodiment of a method 4000;

FIG. 5 is a flowchart of an exemplary embodiment of a method 5000;

FIG. 6 is a flowchart of an exemplary embodiment of a method 6000;

FIG. 7 is a flowchart of an exemplary embodiment of a method 7000;

FIG. 8 is a flowchart of an exemplary embodiment of a method 8000; and

FIG. 9 is a block diagram of an exemplary embodiment of an informationdevice 9000.

DETAILED DESCRIPTION

As used herein, an I/O device can comprise any sensory-oriented inputand/or output device, such as an audio, visual, tactile (includingtemperature, pressure, pain, texture, etc.), olfactory, and/ortaste-oriented device, including, for example, a monitor, display,keyboard, keypad, touchpad, pointing device, microphone, speaker, videocamera, camera, scanner, and/or printer, potentially including a port towhich an I/O device can be attached or connected.

As used herein, render means made perceptible to a human, for example asdata, commands, text, graphics, audio, video, animation, and/orhyperlinks, etc., such as via any visual and/or audio means, such as viaa display, a monitor, electric paper, an ocular implant, a speaker, acochlear implant, etc.

As used herein, an information device can be any general purpose and/orspecial purpose computer, such as a personal computer, workstation,server, minicomputer, mainframe, supercomputer, computer terminal,laptop, wearable computer, and/or Personal Digital Assistant (PDA),mobile terminal, Bluetooth device, communicator, “smart” phone (such asa Handspring Treo-like device), messaging service (e.g., Blackberry)receiver, pager, facsimile, cellular telephone, a traditional telephone,telephonic device, a programmed microprocessor or microcontroller and/orperipheral integrated circuit elements, an ASIC or other integratedcircuit, a hardware electronic logic circuit such as a discrete elementcircuit, and/or a programmable logic device such as a PLD, PLA, FPGA, orPAL, or the like, etc. In general any device on which resides a finitestate machine capable of implementing at least a portion of a method,structure, and/or or graphical user interface described herein may beused as an information device. An information device can includewell-known components such as one or more network interfaces, one ormore processors, one or more memories containing instructions, and/orone or more input/output (I/O) devices, etc.

FIG. 9 is a block diagram of an exemplary embodiment of an informationdevice 9000. Information device 9000 can comprise a network interface9100. Network interface device 9100 can comprise a telephone, a cellularphone, a cellular modem, a telephone data modem, a fax modem, a wirelesstransceiver, an ethernet card, a cable modem, a digital subscriber lineinterface, a bridge, a hub, a router, or other similar device.Information device 9000 can be connectable directly and/or indirectly toother information devices via network interface 9100.

Information device 9000 can further comprise a processor 9200. Processor9200 can be a central processor, a local processor, a remote processor,parallel processors, and/or distributed processors, etc. The processorcan be a general purpose microprocessor, such the Pentium III series ofmicroprocessors manufactured by the Intel Corporation of Santa Clara,Calif. In another embodiment, the processor can be an ApplicationSpecific Integrated Circuit (ASIC) or a Field Programmable Gate Array(FPGA) that has been designed to implement in its hardware and/orfirmware at least a part of an embodiment disclosed herein. Processor9200 can make information device 9000 adaptable to perform according toa plurality of instructions.

Information device 9000 can further comprise a memory 9300. Memory 9300can comprise any device capable of storing analog or digitalinformation, for example, a non-volatile memory, volatile memory, RandomAccess Memory, RAM, Read Only Memory, ROM, flash memory, magnetic media,a hard disk, a floppy disk, a magnetic tape, an optical media, anoptical disk, a compact disk, a CD, a digital versatile disk, a DVD,and/or a raid array, etc. The memory can be coupled to a processor andcan store instructions adapted for execution by the processor accordingto an embodiment disclosed herein. Memory 9300 can be adaptable to storeinstructions 9400.

Instructions 9400 can comprise a plurality of instructions written in amachine readable language. Instructions 9400 can be adaptable to processinformation when executed by processor 9200. In an operative embodiment,information used by processor 9200 using instructions 9400 can provideinformation to and/or be modified by the processing operation.

Information device 9000 can further comprise an I/O device 9500. I/Odevice 9500 can be adaptable to allow information device 9000 tocommunicate directly and/or indirectly with other information devicesand/or users.

FIG. 1 is a block diagram of an exemplary embodiment of a system 1000.As illustrated, system 1000 can comprise a controller, such as aprogrammable logic controller (PLC) 1200. System 1000 can comprise amachine and/or process monitorable and/or controllable by PLC 1200.System 1000 can further comprise hardware and/or software adaptable toallow a user to communicate with PLC 1200. PLC 1200 can be acommercially purchased PLC. Alternatively, PLC 1200 can be aninformation device. PLC 1200 can be used to monitor and/or control aprocess, such as an industrial process. For example, PLC 1200 canmonitor and/or control an alarms indicator, relay, sensor, anothercontroller, and/or a motion device, such as a motion controller, such asa stepper motor controller, a servo controller, an actuator controller,etc.; a motion drive, such as a stepper drive, servo drive, etc.; and/oran actuator, such as a stepper motor, servomotor, linear motor, motor,ball screw, servo valve, hydraulic actuator, pneumatic valve, etc.

PLC 1200 can include a central processing unit (CPU) via whichinstructions are processed and appropriate control signals determined.PLC 1200 can further comprise and/or be coupled to an input-output (I/O)device. The I/O device can render information obtained from PLC 1200.The user also can interact with PLC 1200 via the I/O device. As usedherein interact means receiving alerts or notifications, revising orswitching programs, examining control algorithms, and/or modifyinggraphics displays, etc.

A memory device, such as a memory cartridge 1100 can be couplable to PLC1200, either directly or via a network. In certain embodiments, memorycartridge 1100 can be insertable into PLC 1200 and/or directlyconnectable to PLC 1200. The memory device can be non-volatile memory,volatile memory, ROM, random access memory, flash memory, magneticmedia, a hard disk, a floppy disk, a magnetic tape, an optical media, anoptical disk, a CD, a DVD, and/or a raid array, etc. The memory devicecan provide storage for instructions or data usable by the PLC's CPU.

In an exemplary embodiment, PLC 1200 can be couplable to a userinterface device 1300 via a network 1600. Network 1600 can be a public,private, circuit-switched, packet-switched, virtual, radio, telephone,cellular, cable, DSL, satellite, microwave, AC power, twisted pair,ethernet, token ring, LAN, WAN, Internet, intranet, wireless, Wi-Fi,BlueTooth, Airport, 802.11a, 802.11b, 802.11g, and/or any equivalentsthereof, etc.

Via user interface device 1300, the user can interact with PLC 1200.User interface device 1300 can be an information device. For example,via user interface device 1300, the user can monitor a process,connectable to and/or controllable by PLC 1200. The user also caninteract with PLC 1200 via user interface device 1300.

Via network 1600, PLC 1200 can be further couplable to a process element1400. Process element 1400 can comprise a machine tool, a robot, achemical reactor, a stove, a furnace, an assembly machine, a packagingmachine, and/or piece of conveying equipment, etc. In an operativeembodiment, process element 1400 can be controlled, influenced, and/ormonitored via PLC 1200.

The PLC can be further communicable with the user via network interfacedevice 1500. Network interface device 1500 can be a telephone, acellular phone, a modem, a cellular modem, a telephone data modem, a faxmodem, a wireless transceiver, an ethernet card, a cable modem, adigital subscriber line interface, a bridge, a hub, a router, or othersimilar device. Network interface device 1500 can be adaptable to allowthe user to communicate with PLC 1200 while located remotely from thePLC 1200. Via a network interface device 1500, network 1600 can befurther couplable to a peripheral network 1700. Peripheral network 1700can be a public, private, circuit-switched, packet-switched, virtual,radio, telephone, cellular, cable, DSL, satellite, microwave, AC power,twisted pair, ethernet, token ring, LAN, WAN, Internet, intranet,wireless, Wi-Fi, BlueTooth, Airport, 802.11a, 802.11b, 802.11g, and/orany equivalents thereof, etc. etc.

Peripheral network 1700 can be further connectable to a remote userinterface device 1800. Remote user interface device 1800 can be aninformation device comprising an I/O device. In an operative embodiment,peripheral network 1700 can be adapted to allow the user to interactwith PLC 1200. Peripheral network 1700 can allow the user to interactwith PLC 1200 from a location hundreds or even thousands of miles awayfrom PLC 1200. Peripheral network 1700 can be usable to enhanceavailability and reduce programming, managerial, and/or maintenancecosts attributable to PLC 1200 and/or the monitoring and/or control ofprocess element 1400. Process element 1400 can be one of a plurality ofprocess elements.

FIG. 2 is a block diagram of an exemplary embodiment of a data structure2000. An exemplary embodiment of data structure 2000 can comprise aproject file 2100. Project file 2100 can be storable on a memory device,such as the memory cartridge. Project file 2100 can comprise a program2200, a recipe 2300, information indicative of a data log file structure2400, information indicative of a recipe structure 2500, and/or asupport document 2600, etc. Data log file structure 2400 can be storedseparately from a corresponding data log file, which can be stored onany memory device. Recipe structure 2500 can be stored separately from acorresponding recipe 2300. Project file 2100, and/or one or moreelements thereof, can be adaptable to allow the PLC to monitor and/orcontrol a process element.

Program 2200 can comprise a set of machine-readable instructions.Program 2200 can be transferable to the PLC. Program 2200 can beexecutable on the PLC. Program 2200 can be storable in project file2100. In an operative embodiment, program 2200 can be adapted and/oradaptable to facilitate the performance of tasks by the PLC such asdisplaying a process flow, transferring information, storinginformation, processing information, prompting a user for input,controlling a process variable, and/or reporting a process output, etc.

Recipe 2300 can comprise at least one of a plurality of input values,each input value from the plurality of input values corresponding to aprocess variable. Each process variable can be used to monitor and/orcontrol a process via a PLC. Recipe 2300 can comprise values forsettings such as: machine speed, machine size, product type, productcomposition, product size, product labeling, package type, package size,package labeling, a pressure, a temperature, and/or any other relevantprocess parameter. Recipe 2300 can be storable in project file 2100.Recipe 2300 can be communicable to provide settings to program 2200 inorder to render a product makable and/or a process operable using thePLC. Alternatively, recipe 2300 can be communicable to a differentprocessing device and/or software to provide settings to render aproduct makable and/or process operable.

Information indicative of the data log structure 2400 can comprise asymbolic representation of how a data log file is formatted for storageand retrieval. Information indicative of the data log file structure2400 can be storable in project file 2100. Information indicative of thedata log file structure 2400 can comprise a series of values and/orcharacters correlatable to structural characteristics of the data logfile. The data log file and/or the information indicative of the datalog structure 2400 can be storable on the memory cartridge or on anothermemory device. Information indicative of the data log file structure2400 can be adaptable to render the data log file machine-storableand/or machine-readable. Information indicative of the data log filestructure 2400 can be storable separately from the data log file.

Information indicative of the recipe structure 2500 can comprise asymbolic representation of how the recipe is formatted for storage andretrieval. Information indicative of the recipe structure 2500 can bestorable in project file 2100. Information indicative of the recipestructure 2500 can comprise a series of values and/or characterscorrelatable to structural characteristics of the recipe. Informationindicative of the recipe structure 2500 can be adaptable to render therecipe machine-storable and/or machine-readable. Information indicativeof the recipe structure 2500 can be storable separately from the recipe.

Support document 2600 can comprise a textual and/or visualrepresentation of information assimilatable to improve understanding ofthe PLC, the memory cartridge, hardware components related to the PLC,software components related to the PLC, and/or the controlled process,etc. Support document 2600 can be storable in project file 2100. In anexemplary embodiment, support document 2600 can be reviewable by theuser at the user interface device in order to facilitate understandingand/or modifying the PLC, hardware related to the PLC, software relatedto the PLC, the process, the project file, the data log file,information indicative of the structure of the data log file, therecipe, and/or information indicative of the structure of the recipe,etc. Alternatively, support document 2600 can be rendered to the uservia an I/O device connectable to an information device.

FIG. 3 is a flowchart of an exemplary embodiment of a method 3000 forusing the memory device. At activity 3100, a beginning memory segment onthe memory cartridge can be located where the project file or anycomponent thereof can be read from and/or written. Alternatively, thebeginning memory segment can be located on the memory device. In anoperative embodiment, the project file can occupy a single memorysegment. Alternatively, in an operative embodiment, the project file canoccupy a plurality of memory segments. At activity 3200, the projectfile can be provided to the memory cartridge. Alternatively, the projectfile can be provided to the memory device. Providing the project file tothe memory device can allow information contained in the project file tobe subsequently transferred to the PLC. For example, in case of a powerfailure erasing volatile memory in the PLC, certain information erasedfrom volatile memory can be restorable from the project file stored inthe memory device.

FIG. 4 is a flowchart of an exemplary embodiment of a method 4000 forusing the memory device. At activity 4050, the user can request toobtain (e.g., view, hear, have rendered, and/or obtain access to)information stored and/or storable on a memory device. The informationcan comprise programming code, programming code documentation, supportdocumentation pertaining to hardware and/or software relatable to thePLC, process data, recipe code, and/or recipe information, one or moredata logs, etc. The user can potentially improve monitoring, control,and/or management of the PLC and/or at least one process element withthe obtained information.

At activity 4100, the user can be prompted to select a language forrendering the information from a plurality of language choices. The usercan be allowed to provide a selection corresponding to a selectedlanguage. The user can be allowed to make a selection on an I/O deviceconnectable to an information device. Language choices can comprise anylanguage, such as English, German, French, Italian, Spanish, and/orChinese, etc. The user can select the language by providing a user inputcorresponding to a selected language.

At activity 4200, the user input can be received corresponding to aselected language. The user input can be received as a result of a userinteracting with an I/O device connected to an information device. Theuser input can improve communicability of information to and/or from thePLC via transferring the information in a language favored and/or betterunderstood by the user.

At activity 4300, the information can be located on the memory device.The information can be located by the actions of the PLC or anyinformation device directly and/or indirectly connectable to the PLC.Locating the information can facilitate communications between the userand the PLC.

At activity 4400, the information can be provided to the user responsiveto the user input corresponding to the selected language. Theinformation can be provided, in the selected language, to the userinterface device. Alternatively, the information can be provided, in theselected language, to any I/O device and/or any information device.

FIG. 5 is a flowchart of an exemplary embodiment of a method 5000 forusing the memory device. At activity 5100, a first identifying stamp canbe provided for a data log record. The first identifying stamp cancomprise a calendar date and/or a clock time associated with requesting,collecting, receiving, and/or recording the data log record.Alternatively, the first identifying stamp can relate to a process unit,such as a machine, instrument, and/or device, etc., associated with adata log record. For example, the first identifying stamp can be aprocess unit identifier, such as a machine number, a sensor number,and/or an actuator number, etc. In an operative embodiment, the processidentifying stamp can assist the user in analyzing and categorizing datalog records.

At activity 5200, the PLC can allow the user to select a secondidentifying stamp from a plurality of choices. Identifying stamp choicescan comprise various date and/or time elements comprising a year, amonth, a day, a day of week, an hour, a time zone, a minute, a secondand/or a portion of a second, etc. Alternatively, the second identifyingstamp can comprise various numbers and/or symbols relatable to theprocess unit.

At activity 5300, a user input corresponding to a selection of thesecond identifying stamp can be received from the selection device. Thesecond identifying stamp can improve the user's ability to analyze theprocess log record. Alternatively, the second identifying stamp canreduce storage space requirements for a data log record by providing asmaller second identifying stamp as compared to the first identifyingstamp.

At activity 5400, the selected second identifying stamp can be providedto the memory device responsive to the user input. In an operativeembodiment providing the second identifying stamp to the memory devicecan supply information to the user, when the user subsequently analyzesthe data log record, information within the second identifying stamp canbe adaptable to improve the efficiency of analyzing, sorting, and/orotherwise processing information in the data log record.

FIG. 6 is a flowchart of an exemplary embodiment of a method 6000 forusing the memory device. At activity 6100, a first setting can beprovided corresponding to an instruction to erase or to not erase thedata log from the memory device after the data log is read. Theinstruction to erase or not erase the data log file subsequent toreading the data log file can allow a user to more effectively managedata storage and retrieval on the memory device. Erasing the data logfile can provide an assurance that no data log record on the memorydevice has been previously read.

At activity 6200, the user can be allowed to select a second settingcorresponding to an instruction to erase or to not erase the data logfrom the memory device after the data log is read. The second settingcan provide instructions contrary to the first setting. Providing thesecond setting can allow the user improved control over data storageresources.

At activity 6300, the data log can be read from the memory device. Thedata log can then be erased or not erased from the memory deviceresponsive to the user input. Reading the data log can allow the user totransfer information for additional processing and/or storage responsiveto needs to analyze and/or improve the monitoring, control, and/orreporting of the process element controllable by the PLC.

FIG. 7 is a flowchart of an exemplary embodiment of a method 7000 forusing the memory device. At activity 7100, the user can be promptedallowed to select elements of a project file for storage on the memorydevice. The selectable elements can comprise the project file, theprogram, the recipe, information indicative of the recipe structure,information indicative of the data log file structure stored separatelyfrom the data log file, and/or support documentation pertaining to theprocess, the PLC, hardware related to the PLC, and/or software relatedto the PLC.

At activity 7200, a user input corresponding to an option to store atleast one project file element can be received from the selectiondevice. Providing the user with storage options can allow the user tocustomize a storage plan to suit unique system requirements taking intoconsideration such factors as: other means for storing the project file,the size of the memory cartridge, the amount of process data collectedfor storage in the data log file, the frequency of storing process datacollected for storage in the data log file, the number of recipesstorable in the memory device, and/or the amount and/or content ofsupport documentation available, etc.

At activity 7300, project file elements can be written to the memorydevice responsive to the user input. The project file elements can bewritten beginning at a vacant memory segment. Alternatively, projectfile elements can overwrite a previously stored project file.

FIG. 8 is a flowchart of an exemplary embodiment of a method 8000 forusing the memory cartridge. At activity 8100, a first head marker,indicative of a beginning memory segment for a data log record to bewritten, can be located on the memory device. The data log record can beof a size storable on a single memory segment. Alternatively, the datalog record can be of a size storable on a plurality of memory segments.Memory segments usable for data log storage can be spatially and/orlogically contiguous, and/or can be writable sequentially.

At activity 8200, the data log record, which can comprise a second headmarker, can be written to at least the beginning memory segment. Thedata log record can be written on at least one vacant memory segment.Alternatively, the data log record can overwrite at least one memorysegment used by an older data log record. The second head marker cancontain information reflective of a location of a next memory segmentfor storage of a next data log record. In an exemplary embodiment, thedata log file can be written in a logically circular buffer. Thelogically circular buffer can be characterized by data log recordswritten to contiguous memory segments, the buffer commencing at abeginning memory segment. The logically circular buffer can be furthercharacterized by the writing of the next data log record at thebeginning of the buffer when the buffer is full. The next data logrecord can overwrite an oldest data log record written in the logicallycircular buffer. For example, if the buffer is full, the next data logrecord to be written can be written at the beginning of the buffer,thereby overwriting the data log record that was previously at thebeginning of the buffer. The logically circular buffer can comprise acircular buffer wherein memory segments are physically contiguous toeach other.

At activity 8300, the first head marker can be changed to a recordmarker reflective of the data log record written in at least thebeginning memory segment. The record marker, as changed, can beindicative of the successful writing of the data log record comprisingthe second head marker.

After activity 8200 and before fully completing activity 8300, a powerfailure might occur. A power failure occurring before activity 8300 isfully completed can leave a data log file with two head markers turnedon simultaneously. At activity 8400, in an operative embodiment, the PLCcan assure the presence of a single head marker after the power failure,via an error checking technique. The error checking technique can be anones complement method, a Fletcher checksum method, a cyclic redundancycheck method, and/or extended-precision checksum method, etc. The errorchecking technique, possibly coupled with knowledge of the position ofthe records in question and/or the position and/or direction thatrecords are added to the memory device, can identify which record is themost recent, and thereby which head marker is erroneous.

In an operative embodiment, the PLC can disable and/or eliminate theolder, duplicate head marker, or possibly convert the older, duplicatehead marker to a non-head marker resulting in the presence of a singlehead marker in the data log file, that single head marker correspondingto the new record. Changing the value of a binary bit can disable theolder, duplicate head marker. Alternatively, the PLC can inspect andtest a marker, such as a time stamp marker, on each of the data logrecords, to determine the most recently written record.

At activity 8400, the data log record can be read from the memorydevice. In an operative embodiment, the data log record can be read fromat least one memory segment responsive to the data log structure.Information indicative of the data log structure can be storedseparately in the memory device.

Still other embodiments will become readily apparent to those skilled inthis art from reading the above-recited detailed description anddrawings of certain exemplary embodiments. It should be understood thatnumerous variations, modifications, and additional embodiments arepossible, and accordingly, all such variations, modifications, andembodiments are to be regarded as being within the spirit and scope ofthe appended claims. For example, regardless of the content of anyportion (e.g., title, section, abstract, drawing figure, etc.) of thisapplication, unless clearly specified to the contrary, there is norequirement for any particular described or illustrated activity orelement, any particular sequence of such activities, or any particularinterrelationship of such elements. Moreover, any activity can berepeated, any activity can be performed by multiple entities, and/or anyelement can be duplicated. Further, any activity or element can beexcluded, the sequence of activities can vary, and/or theinterrelationship of elements can vary. Accordingly, the descriptionsand drawings are to be regarded as illustrative in nature, and not asrestrictive.

1. A method for utilizing a memory cartridge connected to a programmablelogic controller (PLC), the memory cartridge comprising a plurality ofmemory segments, the method comprising a plurality of activitiescomprising: locating, on the memory cartridge, a first head markerrelatable to a first data log record, the first head marker indicativeof a beginning memory segment for a second data log record to bewritten; and writing the second data log record to at least thebeginning memory segment, the second data log record corresponding to adata log file structure stored separately from a corresponding data logfile on the memory cartridge, the data log file structure structurallydefining the data log file and comprising a symbolic representation ofhow the data log file is formatted for storage and retrieval, the datalog file structure stored as part of a projectile, the project filefurther comprising a PLC program and a recipe structure.
 2. The methodof claim 1, wherein the second data log record comprises a second headmarker.
 3. The method of claim 1, wherein said writing activity causes asecond head marker to be created relatable to the second data logrecord.
 4. The method of claim 1, further comprising: changing the firsthead marker to be a non-head marker.
 5. The method of claim 1, furthercomprising: reading the second data log record.
 6. The method of claim1, further comprising: responsive to a power failure, determining thattwo head markers in the data log file are turned on simultaneously. 7.The method of claim 1, further comprising: responsive to a powerfailure, via an error checking technique, identifying which of tworecords comprising a head marker is most recent in the data log file. 8.The method of claim 1, further comprising: responsive to a powerfailure, via a Fletcher checksum method, identifying which of tworecords comprising a head marker is most recent in the data log file. 9.The method of claim 1, further comprising: responsive to a powerfailure, via an extended-precision checksum method, identifying which oftwo records comprising a head marker is most recent in the data logfile.
 10. The method of claim 1, further comprising: responsive to apower failure, converting a duplicate head marker to a non-head markerin the data log file.
 11. The method of claim 1, further comprising:responsive to a power failure, changing a value of a binary bit todisable a duplicate head marker in the data log file.
 12. The method ofclaim 1, further comprising: responsive to a power failure, inspecting atime stamp marker to determine a most recently written record in thedata log file.
 13. The method of claim 1, further comprising: responsiveto a received user input of an option to erase a read data log file,automatically erasing the data log file from the memory cartridge. 14.The method of claim 1, further comprising: responsive to a received userinput of an option to erase a read data log file, automatically erasingthe data log file from the memory cartridge, the user input receivedresponsive to a prompt, a beginning memory segment the data log fileidentified via a record marker, a last written record of the data logfile identified via a second head marker associated with the second datalog record.
 15. The method of claim 1, further comprising: receiving auser input regarding an option to erase the data log file, the PLCadapted to erase the data log file responsive to the user input afterthe data log file is read.
 16. The method of claim 1, wherein the datalog file is written in a logically circular buffer, the PLC adapted towrite a next data log record at a beginning of the logically circularbuffer when the logically circular buffer is full.
 17. The method ofclaim 1, wherein the second data log record overwrites a memory segmentused by an older data log record.
 18. A method comprising a plurality ofactivities comprising: on a memory cartridge connected to a programmablelogic controller (PLC), writing a first data log record to at least abeginning memory segment of the memory cartridge, the memory cartridgecomprising a plurality of memory segments, the first data log recordcorresponding to a data log file structure stored separately from a datalog file on the memory cartridge, the data log file structurestructurally defining the data log file and comprising a symbolicrepresentation of how the data log file is formatted for storage andretrieval, the data log file structure stored as part of a project file,the project file further comprising a PLC program and a recipestructure, the beginning memory segment located via a first head markerrelatable to a second data log record, the first head marker indicativeof the beginning memory segment.
 19. A machine-readable mediumcomprising computer-executable instructions for activities comprising:locating, on a memory cartridge connected to a programmable logiccontroller (PLC), a first head marker relatable to a first data logrecord, the first head marker indicative of a beginning memory segmentfor a second data log record to be written, the memory cartridgecomprising a plurality of memory segments; writing the second data logrecord to at least the beginning memory segment, the second data logrecord corresponding to a data log file structure stored separately froma corresponding data log file on the memory cartridge, the data log filestructure structurally defining the data log file and comprising asymbolic representation of how the data log file is formatted forstorage and retrieval, the data log file structure stored as part of aproject file, the project file further comprising a PLC program and arecipe structure; creating a second head marker relatable to the seconddata log record; and changing the first head marker to be a non-headmarker.